1. Field of the Invention
The present invention relates generally to a device for separating a lowermost flat product from a stack of flat products, and particularly to a device having at least one sucker cup for removably attaching along a front edge portion of the lowermost flat product and separating the lowermost flat product from a next adjacent flat product in the stack of flat products.
2. Background Information
In the technology of building books, including booklets, magazines, periodicals, and the like, the use of collating systems is well known. These systems typically have a transporting device on which individual flat products, such as signatures or sheets, are gathered to build a book-block set, which then is finished and bound. Typically, a number of feeders are arranged along the transporting device, each of the hoppers comprising a feeding mechanism for feeding an individual flat product from a stack of flat products onto the transporting device, in order to gradually build up the book-block set or to insert a supplement sheet into a pocket of a pocket feeder or into a newspaper arranged in the pocket. Such feeding mechanisms typically employ a sheet-separating device for separating a sheet or other single flat product from a stack of flat products which is arranged in each hopper. The single flat products are typically drawn from the stack at its bottom end.
When the flat products are printed signatures or sheets having a fold, the flat products are typically transported into a hopper with the flat products arranged so that the folded edge of the flat product is the leading edge and the loose edges of the flat product is the trailing edge. After such folded products are fed onto the transporting device, they are preferably arranged with a lateral edge as the leading edge of the flat product before entering the collating device.
A sheet separating device is described, for example, in U.S. Pat. No. 5,664,786, which is herewith incorporated by reference herein. This document describes a rotating separator disk moveable between sheet material articles. A single suction applicator head, or sucker cup, is positioned underneath a front corner portion of a lowermost sheet of material in a stack of sheets. The single sucker cup disengages the corner portion of the lowermost sheet to enable a rotating separator disk to be inserted between the lowermost sheet and a next adjacent sheet in the stack. Grippers 68 and 70 on rotating drum 42 grip the leading edge portion of the lowermost sheet and pull the lowermost sheet from the hopper.
Another sheet separating device is described in U.S. Pat. No. 6,193,229 B1, which is herewith incorporated by reference herein. This document also describes a rotating separator disk moveable between sheet material articles. A single sucker arm having a sucker cup mounted thereon uses a vacuum to draw the leading edge portion of a lowermost signature in a stack of signatures. A separator disk enters to help separate the lowermost signature from the stack of signature. Grippers 26 arranged on a feed drum 16, grip the leading edge of the lowermost signature. Rotation on the drum transports the lowermost signature away from the stack of signature.
A disadvantage of both of these known devices, is that the lowermost sheet or signature is delivered by the grippers to the transporting device with the folded edge as the leading edge. When used together with a collating device, the signatures or folded sheets must enter the collating device with a lateral edge as the leading edge. Thus, an extra process step is involved in rotating the signatures or sheets before enter the collating device.
Another known sheet separating device includes a sucker bar including two sucker cups for attaching along the lateral edge of a lowermost flat product in a stack of flat products. Grippers, disposed on a rotating drum grip the lowermost flat product along the lateral edge and transport the lowermost flat product away from the stack of flat products and to a transporting device with the lateral edge being the leading edge. This device has the advantage that the flat products leaving the separating device are oriented in the correct position to enter the collating device. However, attaching the sucker cups to the lateral edge of the lowermost flat product, especially when the flat product is a folded sheet product or a signature, and/or when thin or poor quality paper is used. Pulling down on the lateral edge of the folded product can cause tearing of the lowermost sheet, or imperfect separation of the lowermost product. In the latter case, the feeding mechanism may jam, and the process must be paused until the jam has been cleared again.
The present invention provides a device for separating a lowermost flat product from a stack of flat products. The device includes at least one sucker cup moveable so as to removably attach along a front edge portion of the lowermost flat product and to separate the lowermost flat product from a next adjacent flat product in the stack of flat products and a gripper configured for gripping the lowermost flat product along a lateral edge and for transporting the lowermost flat product away from the stack of flat products.
The device may also include a separator element insertable in a space defined between the lowermost flat product and the next adjacent flat product. The flat products may be signatures and/or folded sheets. A hopper for receiving the flat products and for supporting the stack of flat products may also be included.
The at least one sucker cup may be connected to a sucker bar. In addition, the separator element may be rotatably mounted about a separator element axis. A drum disposed below the stack of flat products and rotatable about a drum axis parallel to the lowermost flat product may also be included. The gripper may be connected to a circumferential surface of the drum. The separator element may be disposed adjacent the front edge portion of the lowermost flat product.
The invention also comprises a method of separating a lowermost flat product from a stack of flat products. The method includes the steps of removeably attaching at least one sucker cup along a front edge portion of the lowermost flat product, moving the at least one sucker cup so as to separate the lowermost flat product from a next adjacent flat product in the stack of flat products, gripping along a lateral edge portion of the lowermost flat product using a gripper, releasing the at least one sucker cup from the front edge of the lowermost flat product and transporting the lowermost flat product away from the stack of flat products using the gripper.
The method may also include inserting a separator element into a space defined between the lowermost flat product and the next adjacent flat product. A hopper may be used for sequentially receiving the flat products and supporting the stack of flat products. The at least one sucker cup may be connected to a sucker bar, and the separator may be inserted from the front edge portion of the lowermost flat product, and may be inserted by rotating the separator element about a separator element axis.
The step of transporting the lowermost product maybe performed using a rotating a drum with the gripper being connected to a circumferential surface of the drum. The flat products may include signatures and/or folded sheets.